Today you've come in to work and have been given a multi-gb file containing millions of rows 
of items, each item is placed into one a number of categories, and you've been asked to 
provide a count of the number of items in each level of each category. 

For instance if there are 3 items in "electronics/computers", 5 in "electronics/audio" and 100 
in "books", then you should return an output like: 

  / (root)                       108 
  books/                         100 
  electronics/                     8 <- 8, because there are 5 under audio, and 3 under computers 
  electronics/audio                5 
  electronics/computers            3 <- 3, because there are 2 laptops & one tablet 
  electronics/computers/tablets    1 
  electronics/computers/laptops    2 
    
For our purposes, assume you have a CSV file organized like this: 

  item_id,name,category 
  1,Apple Macbook Air,/electronics/computers 
  2,The Lord of the Rings,/books 
  3,Salt and Vinegar Chips,/food/snackfoods/potato_chips 
  ... 
  10000000,Something Else,/some/other/random/category 

Write a function that will take a CSV file input in this format, and output a  
summary in a format similar to the one shown above